Thermobellows steam trap



Nov. 7, 1967 SENTARO MlYAWAKl 3,351,282

THERMOBELL OWS STEAM TRAP 5 Sheets-Sheet 1 Filed May 6, 1966 Nov. 7, 1967 SENTARO MIYAWAKI 3,351,282

THERMOBELLOWS STEAM TRAP Filed May 6, 1966 5 Sheets-Sheet 2 Nov. 7, 1967 SENTARO MIYAWAKI 3,351,282

THERMOBELLOWS STEAM' TRAP Filed May 6, 1966 5 Sheets-Sheet Nov. 7, 1-967 SENTARO MIYAWAKI 3,351,282

THERMOBELLOWS STEAM TRAP Filed May 6, 1966 5 Sheets-Sheet 4 Nov. 7, 1967 SENTARO MIYAWAKI 3,351,232

THERMOBELLOWS STEAM TRAP Filed May 6, 1966 5 Sheets-Sheet United States Patent f 3,351,282 THERMOBELLGWS STEAM TRAP Sentaro Miyawaki, 549 Midorigaoka, OaZa-Tarumi, Suita, Osaka-fu, Japan Filed May 6, 1966, Ser. No. 543,115 Claims priority, application Japan, June 19, 1965, 40/136,638, 40/256,639; July 9, 1965, 40/ 31,351 5 Claims. (Cl. 23656) ABSTRACT OF THE DISCLOSURE A shock-proof thermobellows steam trap includes a valve casing, a temperature sensitive housing wall secured to the casing and made of strong rigid metal having high heat conductivity. A thermobellows is within the housing wall and expands and contracts responsive to temperature variations detected by and transmitted through the housing wall. An exhaust valve opens and closes a valve port in the casing responsive to movement of the thermobellows. A fine passage in the housing interrupts propagation of any sudden pressure change directly to the thermobellows to protect from Water-hammering. A buffer valve is secured to the valve stem behind the exhaust valve to close the fine passages in the housing.

This invention relates to a thermobellows steam trap.

Conventional compact thermobellows steam traps, such as those used in central heating systems, comprise gathered thermobellows containing a certain quantity of evaporable liquid airtightly sealed therein and an exhaust valve connected to a movable end of said thermobellows for draining condensate or drain, the opposite end of said thermobellows being secured to a casing or housing, thereby said exhaust valve is opened and closed responsive to the reciprocation of said movable end of the thermobellows depending on variations of the vapour pressure of said evaporable liquid therein, which in turn depends on the temperature variation of the condensate or drain surrounding said thermobellows in said casing or housing. Such thermobellows have advantages in that they are easy to handle and to connect to related piping systems, and that exhaustion of low temperature drain, which may contain gaseous substance, from the thermobellows is carried out safely.

On the other hand, such thermobellows have disadvantages in that pressure variations in the piping system connected thereto are directly reflected on the flexible surface wall of said bellows due to the fact that said bellows are so adapted as to be actuated responsive to a pressure diflerence between the inside and outside of the bellows, which causes expansion and contraction in the flexible Wall of the bellows. Accordingly, if any rapid and substantial pressure variation occurs in the piping system, such as sudden and impulsive pressure variations due to water hammering, then such bellows are apt to be damaged easily. Therefore, the durability of such conventional thermobellows has been low, and accordingly the reliability thereof has not been high. Besides, the phenomena of water hammering take place fairly frequently when one starts up a steam piping system containing low temperature drain therein. When such steam piping systern is going to be started up, the thermobellows provided therein are substantially at their fully contracted positions, and hence if such water hammering takes place and rapid impulsive pressure differences are applied to the thermolbellows in the beginning of the operation, then they are deformed readily and permanently.

In such conventional thermobellows, the temperature of the drain is transmitted to the evaporable liquid in the thermobellows only through gathered surface thereof, and

Patented Nov. 7, 1967 if the latent heat of evaporation of said evaporable liquid is large, the heat sensitivity of such thermobellows is reduced substantially, and sometimes even undersirable time delay is caused in the exhaust valve operation.

Due to above disadvantages, such thermobellows have not been used as universal steam traps for industrial appli cations except in central heating systems.

In short, conventional thermobellows steam traps have following advantages.

1) The construction is very simple, and hence the traps are easy to handle and economical to produce.

(2) The response to variations in the loading conditions is good.

(3) Exhaustion of a large quantity of uncondensed gas, such as air, during starting up operation of a steam system can be handled easily.

0n the other hand, disadvantages of such conventional thermobellows are as follows:

(1) Due to the fact that the bellows are made of thin wall members to obtain suitable flexibility, the mechanical strength of the bellows against sudden pressure variations from outside is very low.

(2) Therefore, upon application of sudden and impulsive pressure variations, such as those due to water hammering in the piping system connected thereto, the thermobellows are sometimes damaged immediately or gathers thereof are deformed permanently.

(3) Such damages and permanent deformations hamper subsequent use of such bellows, and hence the durability and reliability of such thermobellows are low.

(4) Thus, such thermobellows are not suitable for industrial applications as universal steam traps, and they have been used only as heat traps for central heating systems.

The principal object of the invention is to obviate said difiiculties in conventional thermobellows steam traps while retaining aforementioned advantages thereof.

An object of the invention is to provide means for protecting thermobellows against damages due to water hammering by enclosing the outer periphery of said thermobellows by a housing made of solid metallic cylinder having a high heat conductivity while extending the valve stem of an exhaust valve secured to the movable end of said thermobellows through said housing so that the inside and outside spaces of said housing may be communicated each other through a narrow sliding gap between the housing and the valve stem, thereby any sudden impulsive pressure variation in the piping system is prevented from being transmitted directly to the outer periphery of the thermobellows by a high resistance against fluid flow at said narrow sliding gap between the housing and the valve stem.

Another object of the invention is to provide a novel thermostatic steam trap comprising thermobellows having a large heat exchange area to give a highly sensitive heat transmitting characteristics to the evaporable liquid sealed therein and a housing surrounding said thermobellows in order to prevent any damage or buckling of the bellows due to sudden pressure variation in a piping system connected thereto, thereby increasing the freedom of choice of evaporable liquids and improving the applicability of the thermobellows steam trap of the kind in various fields.

Still further object of the invention is to provide a novel butter valve responsive to the generation of sudden impulsive pressure variation in a piping system in order to prevent and interrupt propagation of such pressure variation to the inside space of a housing surrounding the outer periphery of a thermobellows, thereby any damage or buckling of said thermobellows is eliminated completely, thus, the durability of such thermobellows steam trap is considerably improved and it is made possible to use the thermobellows steam trap not only in central heating systerns but in various industries as a universal steam trap.

Another object of the invention is to provide a buffer valve located at the back of a main exhaust valve in order to interrupt the propagation of rapid impulsive pressure variations toward the thermobellows at a communicating opening of a housing surrounding said thermobellows, while retaining the normal sensitivity of the thermobellows, said buffer valve being retained normally open regardless of the operative conditions of said exhaust valve but being closed only upon occurrence of a sudden pressure variation in the piping system connected to said ther" mobellows in order to protect the thermobellows effectively.

For a better understanding of the invention, reference is taken to the accompanying drawings, in which:

FIG. 1 is a vertical sectional view of another embodiment of the invention shown with its exhaust valve closed;

FIG. 2 is a diagrammatic illustration of a modification of the steam trap of FIG. 1;

FIGS. 3, 4 and 5 are vertical sectional views of another embodiment of the invention shown with its thermobellows at fully expanded, intermediate and fully contracted positions respectively;

FIG. 6 is a diagrammatic illustration of an exhaust valve; and

FIG. 7 is a vertical sectional view of still another embodiment of the invention comprising a thermostat having flexible gathers at inner peripheries thereof, shown with its exhaust valve closed.

Referring to FIG. 1, the reference numeral 1 designates a casing of a steam trap, 2 an inlet opening, 3 an outlet opening, 4 a valve port or an exhaust opening, 5 an exhaust valve, 6 thermobellows defining an airtight chamber V to hold a certain quantity of evaporable liquid therein, 7 an adjusting screw, 8 a housing consisting of a rigid metallic cylinder having a high thermal conductivity.

The bottom plate 8a of the housing 3 has an opening at the center thereof to form a narrow sliding gap 10 between said bottom plate 8a and the stem portion of the exhaust valve 5 secured to the movable end of the thermobellows 6, and the condensate or the drain of the steam system connected to the steam trap is communicated between the inside and outside spaces of the housing 8 while passing said drain through said narrow sliding gap 10, and hence the drain is brought into contact with restricted passageways for the flow of the drain, the propagation of sudden impulsive pressure variation, for instance pressure variations due to water hammering in the piping system connected to the steam trap, is effectively interrupted before reaching the thermobellows by means of the head loss due to resistance of said passageways against the fluid flow therethrough.

In the preferred embodiment of the invention illustrated in FIG; 1, a sealed chamber V is formed by holding the peripheral edge of the lower open end 6a of a thermobellows 6 between the bottom edge of the housing 8 and the cover plate 8a in a tightly sealed manner. A nipple 7 is welded to the upper end of the housing 8, and a certain quantity of evaporable liquid is placed in the chamber V through an inlet opening 14- bored at the center of the nipple 7, and then the opening 14 is sealed by suitable means, such as silver soldering. Thereafter, the housing 8 is screwed into the bonnet 11 and secured thereto.

A valve stem 5' is secured by welding to the movable end 16 of the bellows 6, and the stem 5 in turn extends through an opening at the center of the bottom cover 8a of the housing 8 so that the lower end of the stem 5' may be positioned opposite to the valve port 4.

Thus, the housing 8, which is made of solid metal plate having a high heat conductivity, acts as a thermal element provided with a bellows 6 at inner surfaces thereof, and the valve stem 5' is reciprocated vertically responsive to expansion and contraction of the heat sensitive expansive fluid sealed in the chamber V defined i by the housing 8 and the bellows 6 to open and close the valve 5 accordingly.

It'is also permissible to provide heat conductive fins 8b on the outer peripheral surface of the housing 8, as illustrated in FIG. 2.

In the steam trap shown in FIG. 1 or 2, the low temperature drain containing uncondensed gaseous substance such as air, enters into the trap through the inlet opening 2 in the beginning of the operation of the steam system connected to the steam trap, and then proceeds further into the inside space of the bellows 6 through the narrow sliding gap 10 surrounding the valve stem 5' thereby the pressure and the drain temperature of said steam system are applied to the inner surface of the bellows 6 and the outer surface of the housing 8.

Since the drain temperature is low in the beginning of the operation, the vapour pressure in the chamber V of the thermobellows is so low that the pressure in the piping system, which is applied to the bellows 6 through the narrow gap 10, exceeds said vapour pressure in said chamber V, thereby the valve stem 5 is moved upwards to separate the exhaust valve 5 from the valve port 4. Thus, the low temperature drain and air contained therein are exhausted completely through the valve port 4. As high temperature drain is introduced into the steam trap following the exhaustion of said low temperature drain, the outer surface of the housing 8 is heated from outside, thereby the vaporable liquid sealed in the thermal element is heated and the vapour pressure in the chamber V is increased. When said vapour pressure in the chamber V surpasses the pressure in said steam sys tem, which acts on the inner surface of the thermal element, then the bellows 6 is contracted to lower its movable end 16 and accordingly the valve stem 5' downwards and close the exhaust valve 5.

With the valve 5 thus closed, as the drain temperatures are reduced by heat dissipation from the surface of the casing 1 and the bonnet 11, the temperature in the chamber V is also reduced to lower the vapour pressure therein and expand the bellows 6.

The movement of the valve 5 during the closing operation thereof is slow due to the limitation of the velocity of the drain flowing out of the inside. space of the bellows 6 through the gap 10, and hence a buffer action is provided to the closing operation of the valve 5 to eliminate excessive tear and wear of the valve and the valve port.

The steam trap of the invention can be operated repeatedly in accurate response to the drain temperature under normal operative conditions. If any sudden impulsive variations in pressure, such as those accompanying water hammering phenomena occurring frequently during starting up operation ofa steam system, are caused, the propagation of such pressure variation to the bellows 6 is effectively interrupted by means of high resistance against fluid flow at the narrow sliding gap 10, thereby the bellows 6 is protected safely against any damage or buckling due to such sudden impulsive pressure variation.

Thus, the steam trap of the invention as shown in FIGS. 1 and 2 is provided with following features.

(1) The heat sensitivity or heat responsiveness is high due to the fact that the temperature of the drain is transferred to the thermal element from the wide outer surface.

(2) The mechanical strength against sudden pressure variation is high due to the fact that the housing 8 is made of rigid metallic plate having a high heat conductivity to withstand against a sizable external force and against sudden impulsive pressure variations in the piping system connected thereto, and that the sharpness of such sudden impulsive pressure variation is reduced before reaching the bellows 6 by means of high resistance against liquid flow at the narrow gap 10 Besides, such impulsive pressure variation acts on the bellows in a direction to expand them, in which direction the bellows are comparatively strong. Therefore, the thermal element will be hardly damaged by a sudden pressure variation.

(3) The movement of the exhaust valve in its closing operation is properly buffered by the resistance against liquid flow through the narrow sliding gap 10.

(4) Thus, wear and tear of the valve and the valve seat are effectively prevented, and resulting in a long service life of the steam trap. Besides, the steam trap is easy to handle and provided with physical properties suitable for universal application.

In the above embodiment of the invention, it is permissible to use flexible diaphragms at the inner surface of said housing 8 instead of bellows shown in FIG. 1.

FIGS. 3 to 5 illustrate still another embodiment of the invention, in which the bellows 6 are surrounded by a housing 8 secured to the bonnet 11 by a mounting threaded stud 7, and the valve stem 5" extends through an opening provided at the center of the bottom plate 8:: of said housing to form a narrow sliding gap 10 between the stem 5" and the bottom plate 8a. A buffer valve 17 is secured to the valve stem 5" and a valve seat 10' is formed around the lower end of the gap 10 to receive said buffer valve 17. A suitable spacing is normally retained from the valve seat 10 to the buffer valve 17 so that the inside and outside spaces of the housing may be communicated each other through said gap to transfer the temperature of the drain to the thermobellows 6. Upon occurrence of a sudden pressure variation in the piping system connected to the steam trap, the liquid passageway through the valve seat 10' is quickly closed responsive to contraction of the thermobellows 6, thus further propagation of such sudden pressure variation is interrupted prior to entering into the inside space of the housing and exerting ill effects on the bellows 6.

In the steam trap shown in FIGS. 3 to 5, low temperature drain containing uncondensed gaseous substance is exhausted responsive to upward movement of the exhaust valve 5 due to contraction of the thermobellows 6, and the exhaust valve 5 is closed when the drain temperature is increased following the exhaustion of the low temperature drain responsive to expansion of the thermobellows 6. When the exhaust valve 5 is opened responsive to contraction of the thermobellows 6, low temperature drain is introduced into the inside space of the housing 8 to cool the bellows 6 and accelerate the upward movement of the valve stem 5" by further cooling the bellows. On the other hand, when the exhaust valve 5 is closed responsive to expansion of the thermobellows 6, high temperature drain is pushed out of the inside space of the housing 8 to slow down the heating of the bellows 6 and to decelerate the downward movement of the valve stem 5", and hence, the closing stroke of the exhaust valve 5 is damped, and thus a long service life of the steam trap is ensured by reducing wear and tear of the valve 5 and the valve seat 4.

Upon occurrence of sudden pressure variation, especially sudden pressure increase, such pressure variation is once transferred to the thermobellows 6 to cause contraction theerof and the buffer valve 17 is moved upwards to engage with the valve seat 16' to block out the narrow sliding gap 10 to interrupt the drain flow therethrough and thereby to prevent any damage or permanent deformation of the thermobellows 6.

In the valve shown in FIG, 6, there are provided a plurality of leakage grooves 18 on that surface of the buffer valve 17 which contacts with the valve seat 10', said leakage grooves 18 being so shaped as to present high iresistance against liquid flow therethrough when the buffer valve 17 is seated at the valve seat 10' in order to damp the impulsive pressure variation proceeding toward the thermobellows 6. The grooves 18 also serve as communication channels between the inside and outside spaces of the housing 8 once the buffer valve 18 is closed, so that pressure difference between said two spaces may be reduced to allow spontaneous opening of the valve 17. However, the sudden pressure variations due to water hammering generally result in oscillations having a comparatively short period, which depend on the dimensions of the related piping system, including rapid pressure increase followed by rapid pressure drops and vice versa. In most cases, such rapid pressure variations are damped only very slowly, and accordingly, it is possible to do with such leakage grooves 18.

If there is no such leakage grooves 18 provided, the propagation of the initial sudden pressure variation is delayed by the limiting resistance of the narrow sliding gap 10, and the buffer valve 17 is closed by said sudden pressure variation, and as the pressure in the space between the steam trap casing 1 and the housing 8 is reduced, the buffer valve 17 is pushed downwards by the pressure in the inside space of the housing 8 to open the narrow sliding gap 10. After repeating such closing and opening operations of the narrow sliding gap 10, the buffer valve 17 comes to rest at its opened position. Thereafter, the steam trap is operated according to its own heat sensitive characteristics.

FIG. 7 illustrates still another embodiment of the invention, wherein a sealed chamber V is formed by closing both of the lower openings of the outer wall comprising a housing 8 and the lower opening of the inner wall comprising bellows 6 by means of a common cover plate 8a, and a certain quantity of highly evaporable liquid is sealed in said chamber V in a manner similar to that in the device of FIG. 1. The housing 8 is made of rigid metallic material having a very high heat conductivity. Accordingly, the steam trap of FIG. 7 has excellent operative characteristics similar to those of the device of FIG. 1, and the bellows 6 in this embodiment is also well protected against sudden impulsive pressure variations. In this embodiment, the buffer valve 17 is formed as an integral part of the exhaust valve 5 at the back thereof, however, it is of course permissible to use a separate buffer valve 17 as shown in FIGS. 3 to 5.

As described in the foregoing, according to the invention, the propagation of sudden impulsive pressure variations, such as those due to water hammering, which occur rather frequently in the starting up operation of a steam piping system, can be interrupted effectively prior to arriving at the surface of thermobellows by means of a device of very simple and economical construction, thereby the thermobellows is completely protected to improve the durability and the reliability thereof and to facilitate the universal application of a steam trap comprising such thermobellows.

What I claim is:

1. A shock-proof thermobellows steam trap comprising; a valve casing including an inlet opening, an outlet opening and a valve port, a temperature sensitive housing wall made of strong rigid metal plate having a highheat conductivity secured to said casing, a thermobellows secured to the inside surface of said housing wall at one end thereof and adapted to expand and contract responsive to temperature variation detected by and transmitted through said housing wall, an exhaust valve secured to a movable end of said thermobellows through a valve stem and disposed adjacent said valve port so as to close and open the valve port responsive to said expansion and contraction of said thermobellows, said valve stem extending through a hole in said housing wall, the hole and valve stem being of a size to provide a narrow sliding gap between said valve stem and the inner surface of said hole, and a buffer valve secured to said valve stem at the back of said exhaust valve so as to block said narrow sliding gap when a sudden pressure change occurs in the valve casing, so that the thermobellows is protected against sudden pressure changes in excess of a certain magnitude.

2. A thermobellows steam trap according to claim 1, wherein said buffer valve is provided with at least one leakage groove on that surface which is to block the narrow sliding gap.

3; A shock-proof thermobellows steam trap comprising; a valve casing including an inlet opening, an outlet opening and a valve port, a cylindrical temperature sensitive housing wall made of strong rigid metal plate having a high heat conductivity secured to the inside of said casing, a thermobello'ws having the lower peripheral edge thereof bonded airtightly to the lower peripheral edge of the cylindrical housing wall so as to form a bell-shaped temperature detecting chamber consisting of an outer shell made of said cylindrical solid housing wall and a contractible inner shell made of said thermobellows, temperature sensitive fluid sealed in said bell-shaped chamber for expanding and contracting said thermobellows responsive to temperature change detected and transmitted through said temperature sensitive wall, and an exhaust valve secured to a movable end of said thermobellows through a valve stem and disposed adjacent said valve port so as to close and open the valve port responsive to 2 said expansion and contraction of said thermobellows, said valve stem extending through a hole on said housing wall, the size of the hole and valve stem providing a narrow gap between said valve stem and the inner surface 5 wherein said valve stem is provided with a buffer valve at the back of said exhaust valve so as to block said narrow gap when a sudden pressure change is generated in the valve casing.

5. A thermobellows steam trap according to claim 4,

10 wherein said butter valve is provided with at least one leakage groove on that surface which is to block said narrow sliding gap.

References Cited 15 UNITED STATES PATENTS 1,467,818 9/1923 Smith 236-56 1,846,226 2/1932 Smith 236-56 2,203,110 6/1940 Smith 23656 1 0 2,513,875 7/1950 Johnson 236-56 2,827,077 3/1958 Mitchell 236-56 1 FOREIGN PATENTS 473,063 10/1937 Great Britain. 482,058 3/1938 Great Britain.

of said hole, so that any abnormal sudden pressure change 25 in said casing is effectively damped prior to arrival of said pressure change at said thermohellows by means of high resistance of said small sliding gap against fluid flow therethrough.

4. A thermobellows steam trap according to claim 3,

WILLIAM J. WYE, Primary Examiner. 

1. A SHOCK-PROOF THERMOBELLOWS STEAM TRAP COMPRISING: A VALVE CASING INCLUDING AN INLET OPENING, AN OUTLET OPENING AND A VALVE PORT, A TEMPERATURE SENSITIVE HOUSING WALL MADE OF STRONG RIGID METAL PLATE HAVING A HIGH SEAT CONDUCTIVITY SECURED TO SAID CASING, A THERMOBELLOWS SECURED TO THE INSIDE SURFACE OF SAID HOUSING WALL AT ONE END THEREOF AND ADAPTED TO EXPAND AND CONTRACT RESPONSIVE TO TEMPERATURE VARIATION DETECTED BY AND TRANSMITTED STHROUGH SAID HOUSING WALL, AN EXHAUST VALVE SECURED TO A MOVABLE END OF SAID THERMOBELLOWS THROUGH A VALVE STEM AND DISPOSED ADJACENT SAID VALVE PORT SO AS TO CLOSE AND OPEN THE VALVE PORT RESPONSIVE TO SAID EXPANSION AND CONTRACTION OF SAID THERMOBELLOWS, SAID VALVE STEM EXTENDING THROUGH A HOLE IN SAID HOUSING WALL, THE HOLE AND VALVE STEM BEING OF A SIZE TO PROVIDE A NARROW SLIDING GAP BETWEEN SAID VALVE STEM AND THE INNER SURFACE OF SAID HOLE, AND A BUFFER VALVE SECURED TO SAID VALVE STEM AT THE 